1. Field of the Invention
The invention relates to a packaging structure for a semiconductor package having a functional element and a through-hole interconnection that connects the front side and the back side, and to a method for manufacturing thereof.
2. Description of Related Art
In a related art technique for packaging a functional element such as a semiconductor light receiving sensor, a functional element is typically contained in a sealing container made of a ceramic or a resin and is then sealed. An example of this related art technique is shown in FIG. 5 (see Japanese Unexamined Patent Application, First Publication No. 2001-351997, for example).
A semiconductor package 40 shown in FIG. 5 includes a semiconductor substrate 41, through-hole interconnections 45b, a sealing material 47, and an optically transparent protecting member 46. A light receiving element 44a including microlenses 44b is provided on the semiconductor substrate 41 for enhancing light-gathering efficiency, and is electrically connected to the outside of the semiconductor package 40 via the wiring 44c and the through-hole interconnection 45b. 
The optically transparent protecting member 46, such as a glass plate, is bonded using adhesive above the semiconductor substrate 41 via the sealing material 47 while keeping a certain distance with the light receiving sensor 44a and the microlenses 44b so that the protecting member 46 does not come in contact with the light receiving sensor 44a and the microlenses 44b. The sealing material 47 is cured after being applied so that the sealing material 47 continuously surrounds the light receiving sensor 44a while not covering the light receiving sensor 44a, and that the protecting member 46 does not come in contact with the light receiving sensor 44a and the microlenses 44b. This sealing material 47 secures the optically transparent protecting member 46 to semiconductor substrate 41 in order to mechanically protect the light receiving sensor 44a and the microlenses 44b as described above. At the same time, it functions as a shield for protecting the light receiving sensor 44a and the microlenses 44b from the surrounding environment.
Procedures to manufacture such a semiconductor package will be described below.
First, the light receiving sensor 44a, a driving circuit (not shown) for the light receiving sensor 44a, a circuit (not shown) for processing output, a wiring circuit 44c, or the like, are fabricated on the semiconductor substrate 41 using typical semiconductor manufacturing techniques.
Next, non-penetrating trenches are defined in portions of the semiconductor substrate 41 corresponding to the wiring circuit using anisotropic etching or the like, and an insulating layer (not shown) and the through-hole interconnections 45b that are made of a conductive layer connecting to the wiring circuit portion 44c are deposited inside the trenches.
Then, the sealing material 47 is disposed on one surface of the semiconductor substrate using a suitable method, such as screen printing or dispensing method or the like, so that the sealing material 47 continuously surrounds the light receiving sensor 44a while not covering the light receiving sensor 44a. 
Next, the optically transparent protecting member 46 that has almost the same two-dimensional size as that of the semiconductor substrate is bonded to the sealing material 47, and the sealing material 47 is cured by the application of heat or ultraviolet light or the like.
Then, the back side of the semiconductor substrate 41 is etched until the through-hole interconnections 45b that have been formed previously are exposed.
Finally, numerous semiconductor packages 40 are obtained by dicing the semiconductor substrate 41 into a predetermined size.
On side surfaces of a thus obtained semiconductor package, the sealing material 47 that bonds the semiconductor substrate 41 and the optically transparent protecting member 46 together is exposed. A synthetic resin is typically used for the sealing material 47, and some synthetic resins do not necessarily exhibit sufficient sealing property, moisture resistance, chemical resistance, or other properties. Consequently, a semiconductor element that stably operates and has an extended life is difficult to obtain.